I got my gloves in yesterday (size L) and am having the same problem with them rubbing my knuckles, but I figured out what's causing it. The way the leather is wider where it's sewn down to make the finger loops is causing the leather to fold under my middle knuckles when I punch, and is basically stabbing them because my fingers aren't fat enough to fill the finger loops so they won't fold (my hand length fits the gloves perfectly, just not my finger thickness).
I THINK putting some cotton material in the finger loops (where the back of my fingers would sit) will remedy the problem for me, so I'm going to try that first. Otherwise, it's time to do some cutting to make the finger loops smaller.
They fit and feel great otherwise though :icon_chee